The Role of the Future in Quantum Theory

TL;DR

This paper proposes that incorporating a final boundary condition in quantum theory, alongside the initial state, can resolve interpretation issues and explain the emergence of classicality in the universe without modifying the theory.

Contribution

It introduces a framework where a future boundary condition complements the initial state, clarifying quantum interpretation and the transition to classical physics.

Findings

Final boundary conditions help define allowed histories in quantum theory.

The approach explains the emergence of classicality in the universe.

Disputes the need for modifications to quantum theory for interpretation.

Abstract

Interpretation problems are eliminated from quantum theory by picturing a quantum history as having been sampled from a probability distribution over the set of histories which are permitted by all relevant boundary conditions. In laboratory physics, the final measurement plays a crucial role in defining the set of allowed histories by constraining the final state to be an eigenstate of the measurement operator. For the universe itself, a final boundary condition can play a similar role. Together with the special big bang initial state, the final constraint may ensure that the universe admits a classical description in the asymptotic future. Acknowledging the role of a future constraint dispels the mysteries of quantum theory without any amendment to the theory itself.